We finally took the 'new' Strat for its first free service today.
They said the bridge was a bit high and they thought that could be causing some of my intonation problems. Also the strings are 9s so I've asked for 10s and agreed to adjusting the bridge a bit lower (so it's lying a bit flatter - but not completely flat like the Mexican Strat).
My husband suggested I ask about volume pedals while there and they had a Boss FV-50 which wasn't too expensive so we bought that and I've had a brief try at it with the Mexican Strat but realise it'll take a bit of getting used to. I've managed to adjust the trem arm of the Mexican Strat now too and it has a really nice tone - a bit wasted on a learner like me at the moment but I'm sure it would sound fantastic if played by an expert. It's a really nice guitar and secondhand - think it's from 2004 from the serial number.
I also changed the acoustic strings for the 3rd time last night reducing the time taken from about an hour and a half to 45 minutes and only destroying one string and only needing one bandaid (from poking the string into my fingers) so I'm improving there too (although I've somehow dropped another plectrum in it and can't remove it).
Anyway we'll collect the Strat on the weekend and hopefully it will sound better. (If not, I have a lot of work to do on my technique - but I don't have as many problems with intonation on the Mexican Strat so maybe it isn't all user error).
Best wishes
Rosemary